willow. 277 



The male tree should be selected for this 

 purpose, because the female tree quickly sheds 

 its catkins. 



The silver-leaved willow, alba serica, should 

 be planted for the contrast it forms with dark 

 evergreen shrubs, and the rosemary-leaved 

 species may also be intermixed with great ad- 

 vantage in many situations. 



These species of trees are very interesting 

 to the botanist. In the Linnean system they 

 are ranged in the 22d class, called Dicecia, 

 from the Greek, meaning two houses, because 

 this class includes the unisexual plants, viz. the 

 male and female flowers being produced on dif- 

 ferent roots or distinct trees. This class, there- 

 fore, in some respects, assimilates the animal 

 and vegetable economy ; for in the plants which 

 are perfectly dioecious, it is known that the 

 female plants produce no fertile seed, without 

 the proximity of the male plant when in 

 flower. For some curious instances of this 

 fact we refer the reader to our history of the 

 date-bearing palm-tree in the Pomarium Bri- 

 tannicum. 



The galls on the leaves of willows are 

 usually of a roundish or oblong figure, and 

 equally protuberant on each side of the leaf, 

 and of a pale green at first ; but afterwards 

 of a yellowish, and finally of a red colour. 



t 3 



